1. Biology Department, Colorado State University, Fort Collins, CO 80521, USA
2. Center for Tropical Research, Institute of the Environment and Sustainability, University of California, Los Angeles, CA 90095, USA
3. Raptor Research Center and Department of Biological Sciences, Boise State University, Boise, ID 83725, USA
4. Intermountain Bird Observatory, Department of Biological Sciences, Boise State University, Boise, ID 83725, USA
5. Department of Bird Migration, Swiss Ornithological Institute, 6204 Sempach, Switzerland